No Man's Land is where you suffer unnecessarily, make lots of noise and ultimately accomplish nothing.

I agree that your statement is a fair take-away for well-trained athletes, but I think it ignores the nuances of the book's advice for beginners.

Here's what the book has to say:

For the well-trained… [zone 2] carries with it a burden of fatigue unworthy of its benefits. Zone 1 will therefore make up the bulk of your base training if you have a very strong background of aerobic endurance training.

However, for those with little aerobic training history (referred to as Aerobic Deficiency Syndrome) this zone [zone 2] can be used for virtually all aerobic base training. The reason is that the pace at this intensity will be quite slow and therefor [sic] there will be little accumulation of neuromuscular fatigue and this effort level won’t even feel like training.

—Training for the New Alpinism, first edition, page 59